Railway vehicle body frame structures that include vertically and horizontally arranged frame members joined to the interior face of an outer panel are generally used (see, for example, Patent Documents 1 and 2). To ensure the flatness of the outer panel by suppressing the buckling and out-of-plane deformation of the outer panel caused by welding distortion and passenger load, various types of arrangements of frame members and various types of joining methods are used in such body frame structures. In the body frame structure described in Patent Document 1, the vertically and horizontally arranged frame members are reduced in number, and horizontal or vertical ribs are disposed on the interior surface of the outer panel so as to be densely arranged in regions surrounded by the frame members and are weld-joined thereto by spot welding. In the body frame structure described in Patent Document 2, a joint structure in which end portions of discontinuous frame members are joined to a continuous frame member by a joint plate is used at many intersections of the vertical and horizontal arranged frame members. In another conventional example shown in FIGS. 4A and 4B, vertical and horizontal frame members a and b are arranged such that the number of intersections is reduced to reduce the number of divided frame members, and the number of the frame members a and b or the area ratio of the frame members a and b with respect to the outer panel c is increased.
[Patent Document 1] Japanese Patent Application Laid-Open No. Hei 5-262228.
[Patent Document 2] Japanese Patent Application Laid-Open No. Hei 9-30414.